It is well known in the art to utilize an acrylic polymer, such as one having substantially the characteristics of polymethylmethacrylate, as the base material for an artificial implant. Note, for example, my U.S. Pat. No. 3,609,867, dated Oct. 5, 1971; and also my copending applications Ser. No. 60,983, filed July 6, 1970, now U.S. Pat. No. 3,790,507, and Ser. No. 186,442, filed Oct. 4, 1971, now U.S. Pat. No. 3,789,029.
As is known, acrylic polymers, such as polymethylmethacrylate, have many characteristics that make them highly desirable for use as an artificial implant, which characteristics include the fact that this material may be readily molded to any desired shape whereby the implant can be "tailor made" to conform identically to the shape of the anatomical structure that is being replaced. Where used as a tooth implant, this type of plastic material has been found to be desirable, since it closely approaches a natural tooth in hardness and rigidity, is not adversely affected by the temperature conditions normally encountered in the human mouth, and has good retention characteristics with respect to color and composition. Also, the chemical and physical properties of a polymer implant can be altered or modified by combining certain ingredients with the polymer, as exemplified by my aforesaid copending applications Ser. Nos. 60,983 and 186,442.
It has recently been found that vitreous carbon has interesting possibilities as an implant material, and particularly as the root portion for dental implants. Vitreous carbon has the advantage of being a highly inert material, perhaps the most inert material known in implantation procedures, and as such, it is not easily degraded in the oral environment, and produces no obvious adverse reactions within the surrounding tissues. In addition to its chemical inertness, vitreous carbon is light, hard, and has a low coefficient of linear thermal expansion. Also, vitreous carbon unlike metals, is resistant to corrosion at body temperatures and contains no impurities that could become tissue irritants.
On the other hand, vitreous carbon has certain disadvantages insofar as implantation procedures are concerned in that vitreous carbon implants must be pre-formed by a lengthy process and cannot be readily fabricated; and hence an exact fitting replica cannot be easily constructed, whereby in some cases the jaw structure has to be surgically modified so as to render the carbon implant acceptable. Also, since vitreous carbon is an extremely brittle material, implants made of this material are subject to fracture and breakage. In addition, vitreous carbon is incompatible with metals, and carbon implants therefore cannot easily be processed upon metal strengtheners, but rather metal can only be glued or cemented to effect a connection to a vitreous carbon implant. Another disadvantage is that a vitreous carbon implant appears to form no periodontal-like membrane.
It has now been found, however, as per the present invention, that by combining an acrylic polymer, such as polymethylmethacrylate, with vitreous carbon, in certain proportions and by using certain methodology, a highly desirable artificial implant may be obtained.
It is therefore a primary object of the present invention to provide an artificial implant that is readily formable to any desired shape, that is not adversely affected by normal temperature changes, is relatively hard and strong but is not unduly brittle, and which is highly inert, whereby no adverse reaction takes place within the surrounding tissues.
It is a further object to provide an artificial implant about which forms a periodontal-like membrane that more closely approaches that of a natural tooth.
Still a further object is the provision of an implant of the character described wherein by using a particular form of vitreous carbon a desired degree of porosity is imparted to the composition, thereby resulting in improved connective tissue attachment with the surrounding host.
Another object is the provision of an implant designed to be used as the root portion of an artificial tooth, the composition of the implant being such as to effectively receive and fuse with a polymer crown.
Other objects, features and advantages of the invention will become obvious as the description thereof proceeds.